There's a surprise inside these treats: marshmallow "lava" erupting from bright-red cake. They're best eaten the day you make them, but cool completely before serving: The marshmallow creme gets quite hot.

2. In a mixing bowl, stir together the yellow cake mix (large packet) and baking soda. Add the cocoa cake mix (small packet), eggs, buttermilk, food coloring, and vanilla. Beat with an electric mixer on low speed until blended, then on high for 2 minutes.

3. Spoon batter into prepared muffin cups, filling them three-quarters full. Spoon a generous teaspoonful of marshmallow creme into the center of each cup. Top with a teaspoonful of batter. Do not smooth the batter out.

4. Bake cupcakes for 18 to 20 minutes, or until tops spring back when lightly touched. Cool for 5 minutes, then turn cakes out onto a wire rack to cool completely. Repeat with remaining batter and creme.